Optical transmission methods are being increasingly used in telecommunications. For this purpose, reliable and inexpensive optoelectronic modules are required, for example as transmitter, receiver or regenerator (“transceiver”).
Such a module, produced by the so-called SiOB (silicon optical bench) technology is disclosed in the article entitled “Low-Cost/High Volume Laser Modules Using Silicon Optical Bench Technology” by J. W. Osenbach et al., Electronic Components & Technology Conference 1998, pages 581-587. It comprises a silicon substrate with metallic solder pads and conductor tracks applied thereto. A laser chip and a photodiode are soldered onto the substrate, while a spherical lens is mounted on the substrate by means of so-called AlO bonding. AlO bonding is understood as meaning a procedure in which a silica (silicon oxide, SiO2) body is pressed at high temperature onto an aluminium layer applied to the substrate. This produces a chemical bond between the SiO2 and the Al.
A disadvantage of the known module is that the high processing temperatures necessary during bonding results in a degradation of the semiconductor chips (laser, photodiode) already mounted. In addition, it makes necessary precisely produced V-grooves for mounting the spherical lens in the correct position.
In an alternative mounting method, the spherical lens is glued on. This has the disadvantages that the adhesive compound has inadequate long-term stability and the optical quality of the module is reduced by outgassing of volatile reaction products of the adhesive.
The object of the invention is therefore to provide a mounting method for a spherical lens on an optical substrate, which method does not have the disadvantages described. Further objects of the invention are to provide a spherical lens suitable for such mounting and an electrooptical module comprising such a lens.